In the UMTS (Universal Mobile Telecommunications System) network, the specifications of long term evolution (LTE) have been drafted for the purpose of further increasing high speed data rates, providing lower delays and so on (see non-patent literature 1). Successor system of LTE—referred to as “LTE-advanced” (also referred to as “LTE-A”)—have been under study for the purpose of achieving further broadbandization and increased speed beyond LTE, and the specifications thereof have been drafted as LTE Rel. 10 to 12.
The system band in LTE Rel. 10 to 12 includes at least one component carrier (CC), where the LTE system band constitutes one unit. Such bundling of a plurality of CCs into a wide band is referred to as “carrier aggregation” (CA).
In CA of Rel. 10 to 12, uplink control information (UCI) to be transmitted from a user terminal is transmitted in an uplink control channel (PUCCH). Also, when the PUCCH and the PUSCH have to be transmitted at the same time while simultaneous transmission of an uplink control channel and an uplink shared channel (PUSCH) is not configured, the user terminal multiplexes all the uplink control information on the PUSCH (piggyback).